Discharge nozzles with a view to reducing the noise of the jet



J. H. BERTIN 2, 5 DISCHARGE NOZZLES WITH A VIEW To REDUCING THE NOISE OF THE JET 2 Sheets-Sheet 1 March 7, 1961 Filed D60. 30, 1957 Ital/(11%? few m Mamh 1961 J. H. BERTIN 2,973,825

DISCHARGE NOZZLES WITH A VIEW T0 mums THE NOISE OF THE JET Filed Dec. :0. 1957 2 Sheets-Sheet 2 United States Patent DISCHARGE NOZZLES WITH A VIEW TO REDUCING THE NOISE OF THE JET Jean H. Bertin, Neniily-sur-Seine, France, assignor to Societe Bertin et Cie (Societe a Responsabilite Limitee), Paris, France, a French company Filed Dec. 30, 1957, Ser. No. 705,871 Claims priority, application France Jan. 9, 1957 3 Claims. (Cl. 181-43) The exhaust jets of reactors and generally all the gaseous jets of large dimensions discharged at high speed into the atmosphere produce a considerable noise, the effects of which may be a nuisance or even injurious to persons in the vicinity.

In order to reduce this noise, it is desirable to improve and to accelerate the mixture of the jet with the atmosphere, which leads, generally speaking, to an increase in the surface of the mixture between these two media, or alternatively to an increase of the speed of the atmospheric air before it comes into contact with the jet, in order to reduce their relative speeds.

The discharge nozzle which forms the object of the invention enables these two effects to be combined by a simple design of its end portion, and without introducing any deflecting surface liable to cause drag or a loss of thrust from the nozzle.

In this discharge nozzle, the outlet cross-section of the jet is shaped so as to have the form of a slot having a relatively large linear development, which surrounds, on at least two opposite sides, the outlet orifice of a conduit for the passage of atmospheric air.

This latter conduit will preferably have a convergent form so that the atmospheric air comes into contact with the inner portion of the exhaust jet passing out of the slot with a fairly high speed in order to reduce the noise resulting from the subsequent mixture of the air with the exhaust gases, whilst reducing the losses of pressure in the conduit and distributing its admission over a greater surface area.

The description which follows below with reference to the accompanying drawings (which are given by way of example only and not in any sense by way of limitation) will make it quite clear how the invention may be carried into effect, the special features which are brought out, either in the text or in the drawings, being understood to form a part of the said invention.

Figs. 1, 2 and 3 show one form of embodiment of a discharge nozzle in accordance with the invention, seen respectively in end view, in side elevation and in crosssection taken along the line ilk-III of Fig. 2.

Figs. 4, and 6 are similar views of an alternative form of embodiment, Fig. 6 being however a horizontal projection without cross-section.

In accordance with Figs. 1 to 3, the exhaust nozzle comprises an outer wall or tubular casing 1 provided with a flange 1a for coupling it to the circular tube (not shown) which precedes it on the reactor, and is terminated by a rearward edge 1b in the form of a flattened oval. The casing 1 is provided with generally oval lateral apertures forming air intake orifices 6 and 7. An inner wall or casing 3 of double curvature forms two lateral conduits 4 and 5 which bring atmospheric air from the orifices 6 and 7 into the interior of the oblong orifice 2b 7 (see Fig. 3) delimited by the rearward edge 2a of the casing 3. The edge 2a is spaced inwardly from the edge 1b to form therebetween an orifice 2 in the form of a flattened annular slot. The casing 3 may be connected to the outer casing 1 of the discharge nozzle by stmts 3' 2,973,825 iatented Mar. 7, 1961 ice suitably streamlined so as to offer the minimum resistance to the flow of the jet. The casings 1 and 3 are joined at the peripheries of the orifices 6 and 7. The intake orifices 6 and 7 of the conduits 4 and 5 have a total crosssection greater than the internal cross-section of the said oblong orifice 2b, so that the atmospheric air sucked-in by the jet passing out of the slot 2 is set into motion in the conduits 4 and 5 before passing out in contact with the annular jet.

In addition, in this example, a small portion of the reaction jet passes out along the axis of the dischargenozzle through a supplementary orifice 8 in the wall 3. This has the advantage of increasing the suction and the acceleration of the in-drawn air in the conduits 4 and 5 without increasing the noise, by reason of the small crosssection of the said orifice, whilst facilitating the manufacture of the wall 3 with a double curvature.

In the alternative form shown in Figs. 4, 5 and 6, the outlet orifice of the jet comprises two slot elements 10 and 11 which are substantially parallel, this giving greater facility of manufacture. The inner peripheries of the slots 10 and 11 are formed by edges 10a and 11a on a wall 3a with double curvature, and the in-drawn air enters laterally through the notches 12 and 13 and passes out through the entire rectangular section comprised between these inner edges.

In either of these forms of construction, the thickness of the layer of the exhaust jet discharged from the annular slot or from the parallel slots may not be the same at various points.

In the case of a reactor with a re-heat system, the cool ing of the inner wall 30 of the discharge nozzle by the atmospheric air which is carried along with it is sufiicient to cool the walls without any additional arrangement.

Furthermore, the discharge nozzle in accordance with the invention may be mounted with equal ease in the fuselage of the machine and on the wings or in separate engine cowlings.

What I claim is:

1. A silencing nozzle for a gas discharge device comprising a first tubular casing, a second tubular casing within said first casing, said casings having inlet and outlet ends, the outlet ends being in substantially a common plane, and the space between said casings forming a conduit for gas, said first casing having lateral conduit means extending to the interior of said second casing, for the introduction of air.

2. A silencing nozzle as defined in claim 1, said second casing having a centrally disposed gas opening.

3. A silencing nozzle as defined in claim 1, the total cross-section of said lateral conduit means exceeding the cross-section of the outlet end of said second casing.

References Cited in the file of this patent UNITED STATES PATENTS 2,308,059 Decker Ian. 12, 1943 2,396,068 Youngash Mar. 5, 1946 FOREIGN PATENTS 25,383 Great Britain 1906 12,859 Great Britain June 16, 1908 15,178 Great Britain Oct. 27, 1915 440,419 Germany Feb. 7, 1927 796,818 France Jan. 27, 1936 1,111,867 France Nov. 2, 1955 768,553 Great Britain Feb. 20, 1957 OTHER REFERENCES Flight publication: Reduction of Jet Noise," pages 57 to 60, July 8, 1955.

Aviation Age: Jet Noise Can Be Cut by Withington, vol. 25, No. 4, April 1956, pages 48 to 53. 

